[llvm] [GISel] Add a little bit of documentation for G_FENCE. (PR #73722)

[Craig Topper via llvm-commits]

https://github.com/topperc created https://github.com/llvm/llvm-project/pull/73722

None

>From d1ad6ac4140e2308d1d37291a59198a05dea75a3 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Tue, 28 Nov 2023 16:17:52 -0800
Subject: [PATCH] [GISel] Add a little bit of documentation for G_FENCE.

---
 llvm/docs/GlobalISel/GenericOpcode.rst | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/llvm/docs/GlobalISel/GenericOpcode.rst b/llvm/docs/GlobalISel/GenericOpcode.rst
index 6c42ddcaff1eccf..26ff34376fb838c 100644
--- a/llvm/docs/GlobalISel/GenericOpcode.rst
+++ b/llvm/docs/GlobalISel/GenericOpcode.rst
@@ -751,9 +751,10 @@ operands.
 G_FENCE
 ^^^^^^^
 
-.. caution::
+Generic fence. The first operand is the memory ordering. The second operand is
+the syncscope.
 
-  I couldn't find any documentation on this at the time of writing.
+See the LLVM LangRef entry on the '``fence'`` instruction for more details.
 
 G_MEMCPY
 ^^^^^^^^